Process for the cold dressing and drying of leather



Oct. 11, 1932. E. LUCKHAUS 1,831,753

FROCESS FOR THE COLD DRESSING AND DRYING OF LEATHER Filed July 24, 1929 l m mulmu Myer/for: Erna? Luck 40:;

BY: la 6 7M: 144 1 I HTTQRW Y Patented Oct. 11, 1932 UNITED STATES PATENT; OFFICE I ERNST LucKHAns, or DUISBURG, GERMANY, s srenon'ro Rom/1a HAAS COMPANY,

OF PHILADELPHIA, PENNSYLVANIA PROCESS FOR THE COLD DRESSING AND DRYING OF lLJllAlHIllR Application filed July 24,1929, Serial No. 380,485 and iii-Germany November 16, 1928.

The invention concerns a process for the cold dressing and drying of leather. The

hitherto known processes have a number of disadvantages, and in particular in that they entail proportionately a very great loss of time. 7

The invention avoids the disadvantages of the known processes. It consists in that the leather, if necessary, after it has been provided with a layer of fat, is treated in a closed container under reduced pressure with a warm air or gas current. In this way it re sults that the cold dressing and drying of the leather is achieved in a much shorter time. In cold dressing the invention also shows the considerable advantage when the process is carried out at ordinary pressure in place of reduced pressure; the penetrating action of the fat into the leather is, however, considerably increased by the use of reduced pressure.

Preferably not only in the drying but also in the cold dressing the vacuum is temporarily broken with an inflow of warm air, the air pressure thereupon being again reduced, whereby a particularly rapid removal of the moisture is obtained.

Hot dipping and cold dressing are terms used in the trade to designate the processes ordinarily used in leather dressing. Hot dipping is done at temperatures as high as 212 F. on dry leather. Cold dressing is carried out at lower temperatures on moist leather. The process herein described discloses a cold dressing process as the term is used in the art even tho temperatures about 95 to 100 F. are employed in the preferred embodiment of the invention.

In all cases a very considerable shortening of the time otherwise necessary for the cold dressing and drying results, and thus there is obtained by the process a leather fibre which is protected to the utmost extent in its deepest parts and a leather of perfect and outstanding qualities.

In the drawing, an apparatus for carrying out the process is shown in one embodiment in longitudinal and cross section. The container a which may be closed and opened with the aid of the cover 6 is provided with tubes 0 and d, by which the air may be removed from the'container to reduce the pressure, or

whereby it may besupplied thereto. The tube 0 is united to a vacuum conduit, an exhaustion pump or the like. Inserted within the container is a carriage having a number of spreading frames for the leather 6. Along the inner walls of the container is arranged a heating coil 7 as well as a number of nozzles g, through which, with the aid of the heating coil 7 or of other means, a heated air or gas stream is led into the interior of the container.

Example 1.-Tanned hide strips known as butts are smeared with 15% (calculated in respect to the moist material) of a dressing material consisting of a mixture of fat and train oil on the flesh side. The butts are then treated in the apparatus described above at about 35 C. under a pressure of 700 millimeters for 3 hours. The greasing mixture may be any of those ordinarily used in dressing leather. My invention, however, does not depend on the dressing material used. The temperature may be higher if higher melting greases are used. It can readily be seen that the pressure can be reduced to a point much below that mentioned without departing from the spirit of the invention.

Example 2.-Butts which have been greased according to my process and in my apparatus or in any other manner in any apparatus may now be dried at 35 to 40 C. under a pressure of about 600 millimeters for about ten hours. After this time the leather shows, without its darkening or being short, a normal moisture content of about 15% of water.

I claim 1. Method of treating skins in the production of leather comprising coating said skins with a fatty dressing material and subjecting said coated skins to the action of gas heated above normal temperature and under a pressure below atmospheric pressure.

2. Method of treating skins in the production of leather comprising coating said skins on the flesh surface with fats and subjecting said coated skins to the action of gas heated above normal temperature and under pressure below atmospheric pressure.

3. Method of treating skins in the production of leather which comprises coating said skins with a fatty dressing material, subjecting said coated skins in a container to a pressure below atmospheric and to a gas heated above normal temperature and at intervals breaking the Vacuum by allowing Warm gas to flow into the container.

4. Method of treating skinsin the produc- 7 tion of leather which comprises coating said skins with a fatty dressing material and; subjecting said coated skins to, the action: of a gas at a temperature of substantially 30 to 40C. and. a pressure of substantially 6100 130 700 millimeters. v

In testimony whereof I have signed my name to this specification.

I J LUCKHAUS.

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